Interpretive Summary: This is a summary of a symposium talk given at the annual meeting of the Society for Invertebrate Pathology in 2001. Nosema disease of parasitoids is a serious problem affecting insect IPM programs and has been studied extensively by scientists with USDA's Center for Medical, Agricultural and Veterinary Entomology. Because the disease is transmitted from infected mothers to their offspring, this is the best place to block the disease. Treating infected parasitoid females with antibiotics or short exposures to high temperatures are effective ways to block transmission from mothers to offspring.

Technical Abstract:
In recent years, Nosema infections have been found in several economically important genera of parasitoids, including Muscidifurax, Spalangia, Encarsi and Tachinaephagous. Infection rates are low in the field but are rapidly amplified under mass-rearing conditions. Infected parasitoids typically ha short lifespans, long immature development times and low fecundity compared dto healthy individuals. Inadvertent releases of infected parasitoids resu in the introduction of massive levels of disease into natural systems where such infections are otherwise rare. The infections are easy to detect and can be prevented in new colonies by good sanitation. The Pasteur method ca be used to eliminate disease when infection rates are low. Differences in development times between healthy and infected parasitoids can also be exploited by defining diagnostic windows of times when mostly healthy parasitoids will emerge. Heat shock is an effective disease management too ofor M. raptor but not for T. zealandicus because the latter species cannot tolerate high temperatures. Treatment of immature parasitoids with gamma radiation kills the parasitoids before any therapeutic effect of treatment can be realized. Maternal transmission can be partially blocked by allowin newly emerged parasitoids to feed for several days on honey treated with 3percent rifampicin (M. raptor, T. zealandicus and Encarsia) or albendazole (M. raptor).